Residual magnetism occurs in materials that acquire magnetic properties when placed in a magnetic field and retain magnetic properties even when removed from the magnetic field. Residual magnets are often created by placing steel, iron, nickel, cobalt, or other soft magnetic materials in a magnetic field. The magnetic field is often generated by running current through a coil of wire placed proximate to the material. The magnetic field generated by the coil orders and aligns the magnetic domains in the material, which is a building block for magnetic properties. Once the material is magnetized and the magnetic field is removed, the magnetic domains remain ordered, and thus, the material retains its magnetism. The magnetization retained in the material after the magnetic field is removed is called the residual or remanence of the material, which depends on the properties of the applied magnetic field and the properties of the material being magnetized. Residual magnets can be considered to be irreversible or reversible, depending on how easily the material can be demagnetized. The residual field of a permanent magnet cannot be easily demagnetized by applying a magnetic field. After a magnetic field is applied to a permanent magnet and then removed, the residual field of the permanent magnet will fully restore itself. Therefore, a permanent magnet is a reversible magnet. An irreversible magnet, also referred to as a residual magnet or a temporary permanent magnet, requires the form of a closed magnetic path (e.g., a ring) in order to set and maintain a residual magnetic field. The residual magnetic field is set by applying a magnetic field to the irreversible magnet. However, the residual magnetic field remains after the magnetic field is removed. The irreversible residual magnet can easily be demagnetized by a magnetic field. After a magnetic field is applied to the residual magnet and then removed, the residual field will not restore itself like the permanent magnet. Therefore, a residual magnet is an irreversible magnet. The irreversible residual magnet will also lose its residual field if its closed magnetic path is opened. Even when the magnetic path is closed again, the residual field of the irreversible residual magnet will not restore itself. Magnetic air gaps can exist to a certain size as part of the closed magnetic path of an irreversible residual magnet and still provide a useful amount of residual magnetic load. The smaller the magnetic air gap, the closer the residual load approaches that of an uninterrupted or completely closed magnet path. Herein, the residual magnetic devices described shall be considered irreversible residual magnets, as defined above.